Type A influenza virus continued to be a major agent of respiratory illness in the population. In addition to type A influenza virus, an even larger number of isolates of Type B influenza virus were made in the winter of 1979-1980. A successful vaccine which could control both of these agents wuould eliminate a large proportion of severe respiratory illness, particularly in the aged and those with compromised respiratory systems. Localization of antigenic sites to specific segments of the hemagglutinin should be of considerable aid in designing synthetic vaccines in the future. The hemagglutinin subunits, HA1 and HA2 have been isolated from type A influenza virus and are being characterized by direct protein sequencing. Fragments of the hemagglutinin subunits are being derived by cyanogen bromide cleavage. Microsequencing is being performed through the use of a Quadrol-Polybrene program and analysis of PTH residues following back hydrolysis and analysis of the amino acids through the o-phthalaldehyde amino acid analyzer. Fragments which are characterized will be used as immunogens to assist in determining antigenic sites. Adjuvants and/or liposomal incorporation will be employed to maximize antibody response. Antibody response will be measured by examination for blocking activity in the hemagglutination assay as well as by the ELISA system. Hemagglutinins have also been isolated from another type A influenza virus (X-53a containing HSwl) and from a type B strain (B/Mass). CNBR cleavage has been performed for the type B hemagglutinin and fragments have been isolated.